In September of last year, financial giant Capital One earned approval from the Fairfax County government for a massive overhaul of its 26-acre campus in Tysons Corner.

Years in the making, the project was one of the largest approved since a new Tysons plan was created in 2010, and it included a 520,000-square-foot corporate headquarters building.

But eight months later, Capital One is scrapping the plans it just got approved. Instead, citing unexpected growth, it filed a new zoning submission for a much larger and more prominent headquarters building to replace the earlier plans.

In the new plans, submitted May 6, Capital One proposes an 800,000 square-foot headquarters that, at 400 feet high, would be 75 feet higher than the previously approved building — and among the tallest that have been proposed for Tysons as the area prepares for more urban development.

The company also changed the location of its headquarters, proposing it for a parcel overlooking the Capital Beltway, where the Fortune 500 company would enjoy high visibility. Previously Capital One had proposed putting two unrelated office buildings there.

Capital One spokeswoman Julie Rakes said in an e-mail that since receiving approval the company realized it would need more space. In 2009, Capital One completed the purchase of Chevy Chase Bank. Headquartered in Bethesda, Chevy Chase had about 250 branches and more than 1,000 automated tellers in the area when it was acquired, contributing to Capital One’s local growth.

“[I]n the past six months, we have better defined and updated our outlook for corporate growth and our newest plans better suit that outlook,” Rakes said.

Capital One’s original plans called for a total of 3.1 million square feet of offices, four high-rise residential buildings with as many as 1,200 units, a hotel and 100,000 square feet of restaurants and retail. Rakes said that mix was not likely to change. “Our revised plans retain almost exactly the same mix of residential, hotel, ground-level, pedestrian-serving retail and commercial office as the rezoning unanimously approved by the Board of Supervisors last fall,” she said.

Capital One is adjusting its plans as Metro’s Silver Line prepares to begin operations near the end of the year. Capital One’s campus, a triangular property between the Beltway and Route 123, is near the easternmost new stop, the McLean station.

Rakes said road work for the new campus could begin in mid-2014 and the company could move into its new headquarters in 2017. A spokesman for the county said officials had not yet reviewed the new submission.